Precision Measurement of the Ratio of the Charged Kaon Leptonic Decay Rates

TL;DR

This paper reports a highly precise measurement of the ratio of charged kaon leptonic decay rates, confirming the Standard Model prediction with minimal uncertainty using data from the NA62 experiment.

Contribution

It provides the most accurate experimental determination of the kaon decay ratio RK, utilizing a large data sample and detailed analysis to reduce uncertainties.

Findings

Measured RK = (2.488 ± 0.010) × 10^{-5}

Result agrees with Standard Model predictions

Analyzed ~150,000 decay candidates

Abstract

A precision measurement of the ratio RK of the rates of kaon leptonic decays K+- --> e nu and K+- --> mu nu with the full data sample collected by the NA62 experiment at CERN in 2007-2008 is reported. The result, obtained by analysing ~150000 reconstructed K+- --> e nu candidates with 11% background contamination, is RK = (2.488+-0.010)*10^{-5}, in agreement with the Standard Model expectation.